Narrative:

I was working controller in charge (controller in charge) along with cab radar; with training going on at local 2 with local 1 combined; and training on ground control. The 3 controllers working that day including me had all taken short breaks to facilitate training. I was working radar; and we were at one of the higher levels of traffic I had worked in a long time. There was lots of aircraft; lots of approaches; and lots of flight following. We get spurts like this often; but they usually do not last as long as this one did. I had 4 aircraft depart the airport south bound 2 IFR and 2 VFR.aircraft Y wanted to go direct to a fix to hold as well; so I put him on a heading and climbed him to 5;000 ft then issued holding instructions. I had aircraft X exit an ir requesting a visual approach so I issued him a heading and climbed him to 6;000 ft. I was trying to keep up with everything; and about this time; the local 2 instructor requested to split local 1 off. The instructor at ground control was the only other controller we had available. He was in the process of getting a new ground controller in; and he eventually grabbed another trainee and split local 1 off. I believe all this occurred within about 10 minutes of the error.when aircraft X was about 6-7 miles south of the airport level at 6;000 ft; aircraft Y was turning back inbound to level at 5;000 ft. At this time I was talking to at least 9 other aircraft. Aircraft X advised they had the airport in sight and I cleared him for the visual approach. I never saw aircraft Y at 5;000 ft. It never crossed my mind that there was a problem. I cannot explain this. When I climbed aircraft X to 6;000 ft I knew he was there; but when I issued the clearance I saw no problem with it. I cannot say that data block overlap was or was not an issue; I do not have any answer for it. I was mentally tired at this time; and my flight strips were all over the place however we had no other options. We all powered through; and I think I eventually got off position about 45 minutes later. It was still a very high work load; and very complex when I gave the position away. I stayed on position about 5 minutes to help the new controller; get strips and a handle on the position before I left. We had no supervisor as one called in sick and one was in a class over at the port fire station; with 3 controllers. At the time; we were so busy; that these resources were not even an option. Other than increasing our staffing; which is what we are trying to do. We have just got our 8th controller within the last week. We are supposed to have 14 controllers; and we have I think 13 trainee's in our facility. We have been working short staffed for so many years. We all are trying so hard to get people trained as we see that that will be the only way we can get this problem resolved. The lack of supervision in the operational areas during this event was a factor however it is quite the norm. With my performance; or for whatever reason just missing aircraft Y; it is a result of trying to do too much; with too little; for too long. I apologize for allowing this to happen on my watch; I do not have an answer for why it happened; and all I can say is that I will try to not let it happen again.

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Original NASA ASRS Text

Title: MWH Tower Cab Radar Controller In Charge reported a loss of separation after inadvertently descending an aircraft into another aircraft.

Narrative: I was working CIC (Controller In Charge) along with Cab Radar; with training going on at Local 2 with Local 1 combined; and Training on Ground Control. The 3 Controllers working that day including me had all taken short breaks to facilitate training. I was working Radar; and we were at one of the higher levels of traffic I had worked in a long time. There was lots of aircraft; lots of approaches; and lots of Flight Following. We get spurts like this often; but they usually do not last as long as this one did. I Had 4 aircraft depart the airport south bound 2 IFR and 2 VFR.Aircraft Y wanted to go direct to a fix to hold as well; so I put him on a heading and climbed him to 5;000 ft then issued holding instructions. I had Aircraft X exit an IR requesting a Visual Approach so I issued him a heading and climbed him to 6;000 ft. I was trying to keep up with everything; and about this time; the Local 2 Instructor requested to split Local 1 off. The Instructor at Ground Control was the only other controller we had available. He was in the process of getting a new Ground Controller in; and he eventually grabbed another Trainee and split Local 1 off. I believe all this occurred within about 10 minutes of the error.When Aircraft X was about 6-7 miles South of the airport level at 6;000 ft; Aircraft Y was turning back inbound to level at 5;000 ft. At this time I was talking to at least 9 other aircraft. Aircraft X advised they had the airport in sight and I cleared him for the Visual Approach. I never saw Aircraft Y at 5;000 ft. It never crossed my mind that there was a problem. I cannot explain this. When I climbed Aircraft X to 6;000 ft I knew he was there; but when I issued the clearance I saw no problem with it. I cannot say that Data Block overlap was or was not an issue; I do not have any answer for it. I was mentally tired at this time; and my flight strips were all over the place however we had no other options. We all powered through; and I think I eventually got off position about 45 minutes later. It was still a very high work load; and very complex when I gave the position away. I stayed on position about 5 minutes to help the new controller; get strips and a handle on the position before I left. We had no Supervisor as one called in sick and one was in a class over at the port fire station; with 3 Controllers. At the time; we were so busy; that these resources were not even an option. Other than increasing our staffing; which is what we are trying to do. We have just got our 8th Controller within the last week. We are supposed to have 14 controllers; and we have I think 13 Trainee's in our facility. We have been working short staffed for so many years. We all are trying so hard to get people trained as we see that that will be the only way we can get this problem resolved. The lack of supervision in the operational areas during this event was a factor however it is quite the norm. With my performance; or for whatever reason just missing Aircraft Y; it is a result of trying to do too much; with too little; for too long. I apologize for allowing this to happen on my watch; I do not have an answer for why it happened; and all I can say is that I will try to not let it happen again.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.